Protein domains mediate protein-protein interaction through binding to short peptide motifs in their corresponding ligands. These peptide recognition modules are critical for the assembly of multi-protein complexes. We have arrayed GST fusion protein, with a focus on protein interaction domains, onto nitrocellulose coated glass slides to generate a protein-domain chip. Domains arrayed on this slide included WW, SH3, SH2, 14-3-3, PDZ, FHA, PH and FF domains. We have demonstrated, using peptides, that the arrayed domains retain their binding integrity. Furthermore, we show that the protein-domain chip can "fish" proteins out of a total cell lysate, these domain bound proteins can then be detected on the chip with a specific antibody, thus producing a binding map for a protein of interest. Panomics, inc. and UT M.D. Anderson Cancer Center now plan to commercialize this protein-domain array. This protein chip will not only detect quantitative changes in proteins, but also promises to identify qualitative differences in protein ligands, thus getting at the heart of signal transduction pathways. In addition, this type of protein-domain array will facilitate the identification of risk factors and chemoprevention targets at the protein level.